Hypertension is a complex disease involving many pathophysiological changes. Important among those changes are alterations in neural and humoral regulation as well as in cell membrane characteristics. Eight principal investigators from 6 departments (3 clinical and 3 pre-clinical) have joined to study these changes. Animal models will include genetic hypertensive rats, DOCA hypertensive rats, sheep, and pigs, the obese dog and the dog to which an increase in lower body pressure is applied. Projects are designed to study the changes which occur during the development of these forms of hypertension and during its recession, when the initiating factors are removed. The goal is to assemble data relevant to the mechanisms responsible for the arterial pressure elevation. Among the specific variables measured will be ion fluxes across membranes, hormone levels (renin, aldosterone, ADH, cortisol, catecholamines) vascular reactivity, central nervous system effects and secretory processes of chromaffin cells. From these integrated projects a better understanding of the initiating factors and sequence of events leading to hypertension will emerge.